Table 2. Effectiveness of COVID-19 vaccination in preventing confirmed SARS-CoV-2 infection and infection outcomes, Navarre, Spain, January–April 2021 (n = 20,961).
| Evaluated outcome and vaccination status | Infections/contacts | Crude RR (95% CI) | Adjusted RR (95% CI)a | Adjusted VE % (95% CI)a |
|---|---|---|---|---|
| Confirmed SARS-CoV-2 infection b | ||||
| Unvaccinated | 6,980/19,580 | Reference | Reference | Reference |
| Vaccinated with 1 dose | 198/869 | 0.64 (0.56 to 0.74) | 0.65 (0.56 to 0.75) | 35 (25 to 44) |
| Vaccinated with 2 doses | 62/512 | 0.34 (0.27 to 0.44) | 0.34 (0.26 to 0.43) | 66 (57 to 74) |
| Relative effect of 2 vs 1 dose | 62/512 vs 198/869 | 0.53 (0.40 to 0.71) | 0.52 (0.39 to 0.69) | 48 (31 to 61) |
| Symptomatic COVID-19 | ||||
| Unvaccinated | 5,306/19,580 | Reference | Reference | Reference |
| Vaccinated with 1 dose | 135/869 | 0.57 (0.48 to 0.68) | 0.58 (0.48 to 0.69) | 42 (31 to 52) |
| Vaccinated with 2 doses | 26/512 | 0.19 (0.13 to 0.28) | 0.18 (0.12 to 0.26) | 82 (74 to 88) |
| Relative effect of 2 vs 1 dose | 26/512 vs 135/869 | 0.33 (0.22 to 0.50) | 0.31 (0.20 to 0.47) | 69 (53 to 80) |
| Hospitalisation due to COVID-19 | ||||
| Unvaccinated | 548/19,580 | Reference | Reference | Reference |
| Vaccinated with 1 dose | 10/869 | 0.41 (0.22 to 0.77) | 0.28 (0.15 to 0.53) | 72 (47 to 85) |
| Vaccinated with 2 doses | 1/512 | 0.07 (0.01 to 0.50) | 0.05 (0.01 to 0.38) | 95 (62 to 99) |
| Relative effect of 2 vs 1 dose | 1/512 vs 10/869 | 0.17 (0.02 to 1.33) | 0.19 (0.02 to 1.49) | 81 (−49 to 98) |
| Symptomatic COVID-19 in 18 to 59 years age group | ||||
| Unvaccinated | 4,120/15,558 | Reference | Reference | Reference |
| Vaccinated with 1 dose | 65/512 | 0.48 (0.38 to 0.61) | 0.49 (0.38 to 0.63)c | 51 (37 to 62) |
| Vaccinated with 2 doses | 16/352 | 0.17 (0.11 to 0.28) | 0.16 (0.10 to 0.26)c | 84 (74 to 90) |
| Relative effect of 2 vs 1 dose | 16/352 vs 65/512 | 0.36 (0.21 to 0.62) | 0.32 (0.18 to 0.55) | 68 (45 to 82) |
| Symptomatic COVID-19 in ≥ 60 years age group | ||||
| Unvaccinated | 1,186/4,022 | Reference | Reference | Reference |
| Vaccinated with 1 dose | 70/357 | 0.67 (0.52 to 0.85) | 0.70 (0.55 to 0.90)c | 30 (10 to 45) |
| Vaccinated with 2 doses | 10/160 | 0.21 (0.11 to 0.40) | 0.23 (0.12 to 0.44)c | 77 (56 to 88) |
| Relative effect of 2 vs 1 dose | 10/160 vs 70/357 | 0.32 (0.16 to 0.62) | 0.33 (0.17 to 0.65) | 67 (35 to 83) |
CI: confidence interval; COVID-19: coronavirus disease; RR: relative risk; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2; VE: vaccine effectiveness.
a RR adjusted by age groups (18–39, 40–59 and ≥ 60 years), sex, contact setting (household or other), major chronic conditions and month.
b Asymptomatic and symptomatic COVID-19.
c Interaction between age group and vaccination with one dose (p = 0.065) and vaccination with two doses (p = 0.375).